The invention relates to open power boats of the type used in fishing tournaments and other recreational boating and particularly to the hull configuration thereof.
In those vee entry boats rated for 140 h.p. and having top speeds in excess of 50 m.p.h., with which the invention is particularly concerned, the choice of hull configuration has conventionally involved various trade offs among the more desirable criteria which include safety and fuel economy on the one hand and high speed performance on the other. The significance of these trade offs is particularly evidenced, by conventional planing hulls, in the individual and collective control of porpoising and stern slippage in high speed turns and in porpoising when running "full out" on plane. In both situations it is necessary to come substantially off speed to achieve the increased wetted area necessary for stern tracking stability and/or to control porpoising. This, of course, produces a significant increase in drag with a concomitant decrease in fuel efficiency both in instituting the stabilizing maneuver and subsequently bringing the boat back to speed. It is the purpose of the invention to resolve these conventional trade offs as related to porpoising and high speed course corrections.
High speed turns are one of the more dangerous boating maneuvers and are particularly unforgiving of the novice boater who has not mastered the "feel" for coordinating trim and throttle adjustments at the inception, and during execution, of the turn. Indeed, it is the rare expert who, even when throttling back from top speed and entering a proper trim adjustment, has not felt unanticipated stern slippage or "chine walk" and porpoising associated with such maneuvers that are wont to capsize the boat.
The prudent boater thus comes substantially off speed to execute a sharp turn. The decrease in speed results in a greater wetted area of the hull, puts more chines in the water and reduces the magnitude, or arc, of the lay over angle which the outer running surface of the hull on the inside of a turn makes with the water surface. The consequence of the latter is that with a lesser arc of downward movement in a given time frame the laying over of the outer running surface into wetting contact does not produce the violent slapping and bouncing from the surface that initiates repeated slapping impacts contributing to the stern slippage that is characteristic of a high speed turn under full throttle where the arc of descent is substantially greater from the full on plane position. Additionally, the greater wetted area in an off speed turn places more of the after running surface wedges in hard water producing a bow down attitude to reduce porpoising in a turn.
The foregoing is the typical performance of conventional vee hulls having the usual planar running surfaces, separated by chines, on either side of the keel line running surface which lateral, planar running surfaces and the central keel line running surfaces, when viewed in transverse section adjacent the aft end of the boat, exhibit a typical V shape terminating, laterally, at outer chines continuous with the sides of the boat.
As related to the present invention, it is important to note that prior art hulls of the type herein contemplated have either been devoid of after wedges or the same have been confined to running surfaces inboard of the outermost running surfaces.
A primary purpose of the after wedges is to reduce porpoising and where the transom is notched or "stepped" as in the present boat the presence of after wedges at the aft end of those running surfaces immediately straddling the stepped portion of the transom are particularly important in the control of high speed porpoising since that is the only portion of the extreme aft end of the boat that is in "hard water". Stated differently, where the after end of the keel line and its associated running surfaces terminate short of the stern (in a transverse "step") the only remaining hull area in hard water, on plane, where a bow down torque can be maximally exerted is at the aft end of the running surfaces immediately straddling the "step". The disclosure in applicant's U.S. Pat. No. 4,233,920 is exemplary.
A necessary trade off for this porpoising control is some increase in drag because of the laminar exit flow disruption from the running surfaces as a function of the downward (stern lifting) flow component imparted by the wedges. Conventionally, this drag factor is substantially uniform across the width of the running surface whose exit ends terminate in wedges since the wedges extend straight across, or perpendicular to, the running surfaces from chine to chine. The laminar flow disruptions created thereby also tend to produce cavitation at high speeds.
In the case of high speed turns the conventional, after center wedge on the outside of the turn is out of the water so that the entire porpoising, or bow down attitude, control falls upon the central wedge or wedges on the inside of the turn. For such central wedges to impose a sufficient bow down torque to control porpoising in a high, or "full out," speed turn the necessary depth and width of the same are such as to impose unacceptable drag during straight running. This for the reason that all the central wedges are in hard water during straight running and it will be apparent that doubling the desired turn drag would drastically reduce top speed performance. Conventional wisdom has avoided the placement of after wedges on the outboard running surfaces because of the likelihood of cavitation when sharply "laying over" in a high speed turn and because of the large increase in drag in the low speed mode when the outer running surfaces are in hard water.